Leak-resistant dry cells



24, 1965 L. F. URRY 3,202,549

' LEAK-RESISTANT DRY CELLS Filed May 1. 1961 ER 5; E ES ZINC CUP [3 :ISHIELDING LAYER 32 INVENTOR.

LE WIS F. U R RY A T TOR/V5 Y United States Patent This invention relates to leak-resistant dry cells of the type having a closed container surrounding the cell proper.

The so-called LeClanche dry cell used for flashlights, portable radios, phototlash and other devices has gone through an evolution of improvements during the past decade or more in an attempt by manufacturers to prevent leakage from the cell during and after its use. Dcspite the many proposals, however, that have been advanced, there still remains a need for a better leakresistant dry cell.

One proposal that has been adopted commercially is to encase a conventional dry cell within a closed container comprising a non-metallic jacket, a false bottom and a metallic top closure. Dificulty has been encountered, however, in preventing the jacket, which has been made from a fibrous material, for example, paper, from being penetrated by liquid exudate which may escape from the cell, for example, in the event the container-electrode becomes perforated during use of the cell. Several proposals have been suggested for overcoming this difticulty by incorporating a liquid-proof barrier into the jacket. Such proposals, however, while protecting the jacket, still permitted liquid to escape from the cell and suffer from the disadvantage that the liquid is free to migrate throughout the cell container, eventually coming into contact with the top and bottom closures where leakage is most apt to occur. Another difiiculty rought about by this migration of liquid has been the possible interference with the proper venting of gas from the cell, resulting in the harmful build-up of pressure within the cell container. Still another dificulty encountered has been that the liquid often becomes a source for the generation of gas, for when it comes into contact between the containcr-elec trode and the bottom of the cell container, they being made from diiterent metals, an electrolytic couple is created which may cause gas to be generated. Various proposals have been advanced for overcoming these difiiculties, for example, by incorporating a seal between the container-electrode and jacket, but these suggestions have not entirely solved the problem and generally have increased the difliculty and cost of manufacturing the cells.

It is therefore the principal object of the invention to provide a construction for a leak-resistant dry cell which will more effectively prohibit leakage.

More specifically, another object is to provide such a construction which will prohibit the migration of liquid throughout the cell container of a leak-resistant dry cell.

Briefly, these and other objects are achieved by the invention which comprises the provision of thin shielding layers ot a plastic material adhered to the whole exterior surfaces and to the upper interior side walls and bottom of the container-electrode of a leak-resistant dry cell.

In the accompanying drawing:

FIG. 1 is a vertical elevation partially in section of a leak-resistant dry cell embodying the invention;

FIG. 2 is a greatly enlarged view of the encircled portion indicated at 2; in FIG. 1;

FIG. 3 is an enlarged detail view taken along the line 3-3 of FIG. 1; and

FIG. 4 is an enlarged detail View taken along the line 44 of FIG. 1.

Referring to the drawing, a dry cell of a conventional construction having a cupped container-anode ill of a consumable metal, for instance, zinc, containing therein 32%,549 Patented Aug. 24., 19%5 a carbon electrode 12 embedded within a depolarizer mix 14- and an immobilized electrolyte 16 suitably in the form of a conventional paste," has provided to the containeranode it) a thin shielding layer 13 as shown in FIG. 1. As best shown in enlarged detail in FIGS. 2 and 4, the shielding layer 15 is firmly adhered to the exterior bottom and side walls of the container-anode 1G. The shielding layer 18 is also applied to the interior side walls of the container-anode It at its upper edges above the depolarizer mix 14 and to its interior bottom wall as best shown in enlarged detail in FIGS. 3 and 4. The shielding layer L8 should be inert to materials in the cell and preferably is composed of a plastic material, for example, vinyl resin, low molecular weight polyethylene, acrylic resins, latex and cellulosic derivatives such as cellulose acetate. A lacquer made from cellulosic derivatives such as cellulose ethers may also be used with success. Also, the plastic material preferably should have good elastic properties, vinyl resin being an excellent example of such material for which reason it is generally preferred. A displaceable inner seal consisting of a wax impregnated paper washer 20 and a soft seal 22 of asphalt, for example, preferably is positioned within the upper edges of the contamer-anode ill. This type of seal serves to entrap liquid within the cell and, being yieldable, also serves to release pressure therein as gas is formed Within the cell. A rigid, non-displaceable inner seal of the type disclosed and claimed in my copending application, Serial No. 106,760, filed concurrently herewith, may also be utilized in the construction of the dry cell shown in FIG. 1.

A preferred top closure for the cell comprises a flanged metal cap 24 fitted on top of the carbon electrode 12 and an insulating washer 26 carried by the metal cap 24 on which rests the inner peripheral edges of a metal washer 28. The outer edges of the washer 28 are locked in engagement with a jacket 39. This construction conveniently provides a venting path for the escape of gas from the cell, for example, from between the displaceable edges of the metal washer 2% and insulating Washer 26. The jacket 3% is non-corrodible, it being composed of a fibrous material, for example, paper, and also has locked to it a metallic false bottom 32 which underlies and is in contact with a portion of the container-anode 10 which is left bare at its bottom exterior Wall.

Having described the construction of a dry cell incorporating the principles of the invention, the advantages made possible by the invention may now be clearly visualized. During or after use of the cell, and especially when the cell has been subjected to severe conditions of discharge, the container-anode 1d may become perforated, in which event liquid is prevented from escaping from the cell and from migrating throughout the cell container by the shielding layer *Iuii. Hence, the difficulties heretofore brought about :by migration of liquid to the top and bottom closures, for example, interference with proper gas venting from the cell, are effectively eliminated. By this construction, it will also :be noted that the use of a liquid-proof barrier heretofore incorporated into the jacket is dispensed with, thereby reducing the cost of manufacturing the cell, since the liquid cannot penetrate the jacket, and the full dry strength of the jacket 3%} utilized in order to resist the build-up of gas pressure within the cell c011- tainer which may develop during operation of the cell.

An important advantage achieved by the invention is made possible by the fact that the shielding layer 18, in the event of perforation of the container-anode d0, prevents liquid from coming into contact with its outer sur 1=aces at least during the useful life of the cell. In contrast with prior dry cell constructions, this construct-ion prohibits an electrolytic or corrosion couple from being formed between the inner amalgamated and outer unamalgamated surfaces of the container-anode 1%, which 3 7 in such prior constructions has resulted in wasteful consumption of anode material and the harmful generation of gas within the cell container.

Also, a further advantage derived from the invention is the additional protection atlorded the inner side and bottom walls of the container-anode 10 by the shielding layer 1-8. In prior dry cell constructions, it has been appreciated thatthese portions of the container-electrode perform no useful purpose, other than to contain liquid within the cell, and in fact are detrimental, for the upper inner edges of the container-electrode, in particular, are

subject to being attacked and corroded during use of the cell. This results in escape of liquid from the containerelectrode,'the harmful generation of-gas and .the possibility of internal short-circuits occurring within the cell. This latter condition has been found to anise from the fact that, when corrosion occurs, anode metal tends to go into solution which eventually deposits over the depolarizer mix in the form of metallic itrees. These so-called so that practically all of the container-anode bottom is protected against corrosion.

The construction of a dry cell embodying the invention lends itself to manufacture in any of several ways. For example, it is conventional inthe manufacture of dry cells to make the container-anode :10 by extruding it from a calotte of zinc. This method formaking the containeranode ll) may be conveniently utilized for incorporating a the shielding layer 18. Thus, the container-anode 10 maybe extruded together with a sheet or film f the plastic shielding material which is firmly adhered to it through the application of heat. This technique, however, can

tests that dry cells of the invention released an amount of gas in a period of several months which equalled that released by cells of a conventional construction over a period of a day.

It will be understood that various changesand modifications may be made in the dry cell construction described herein without departing from the spirit and scope of the invention.

What is claimed is:

1. In a leak-resistant dry cell comprising a cupped container-electrode of a consumable metal having therein a depolarizer mix and electrolyte, the top surfaces of which are disposed below the top open endjof said containerelectrode, and having a thin shielding layer of a plastic material adhered to the exterior side walls and bottom thereof, and a jacket surrounding said cupped containerelectrode and having a top closure locked in liquid-tight engagement therewith, said top closure lacing disposed over the top open end of said container-electrode and dewhich said shielding layers are: composed of an acrylic ,30

resin.

'4. A leak-resistant dry cell as defined iby claim 1 in Which s-aid shielding layers are composed of latex.

5. A leak-resistantdry cell as defined by claim 1 in which-said shielding layers are-composed of a low molecbe used-only forapplying the shielding layer 118 to the exterior bottom and side walls of the container-anode 10. Another technique which may also be utilized for manufactoring dry cells consists of spraying or painting the shielding layer 18 onto the container-anode 10 after it ismadef A number of dry cells embodying the invention have been made and tested tinder severe conditions of use.

These tests demonstrated the elfectiveness of the inven' tion, for cells othenwise identical inconstructi-on but having no shielding layer applied to the container-electrode of the cell evidenced leakage while those. cells embodying the invention showed no evidence of leakage nor of mi ditional tests for determining the amount of gas released by them over a period of time. It was shown in these ular weight polyethylene.

A leak-resistant dry cell as defined by claim 1 in which said shielding layers are composed of a cellulosic material. a

' 7. Aleak-resistant dry cell as defined iby claim '6 in which said cellulosic material is cellulose acetate. 7

8. A leak-resistant dry cell as defined iby claim 6 in which said cellulosic material is a lacquer.

References Cited hy the Examiner UNITED STATES PATENTS 2,146,377 2/39 MacCallum; 2,198,423 4/40 Anthony; 136-132 2,283,379 5/42 MacCallum '136l31 2,5 9,159, 9/51 Gelardin. r 2,708,684 7 5/55 Grieve"; 136-132 x 2,773,920 12/56 Glover 136-l07 2,833,848 5/58 Marty 136182X 7 master: PATENTS 471,425 9/37 Great Britain.

H. MACK, Primary Examiner. 4 JOHN R. SPECK, Examiner.

to the interior bottom' of said 

1. IN A LEAK-RESISTANT DRY CELL COMPRISING A CUPPED CONTAINER-ELECTRODE OF A CONSUMABLE METAL HAVING THEREIN A DEPOLARIZER MIX AND ELECTROLYTE, THE TOP SURFACES OF WHICH ARE DISPOSED BLOW THE TOP OPEN END OF SAID CONTAINERELECTRODE, AND HAVING A THIN SHIELDING LAYER OF A PLASTIC MATERIAL ADHEREED TO THE EXTERIOR SIDE WALLS AND BOTTOM THEREOF, AND A JACKET SURROUNDING SAID CUPPED CONTAINERELECTRODE AND HAVING A TOP CLOSURE LOCKED IN LIQUID-TIGHT ENGAGEMENT THEREWITH, SAID TOP CLOSURE BEING DISPOSED OVER THE TOP OPEN END OF SAID CONTAINER-ELECTRODE AND DEFINING A FREE SPACE ABOVE SAID DEPOLARIZER MIX AND ELECTROLYTE; THE IMPROVEMENT WHICH COMPRISES THE PROVISION OF ADDITIONAL THIN SHIELDING LAYERS OF PLASTIC MATERIAL ADHERED TO THE INTERIOR SIDE WALLS ABOVE SAID DEPOLARIZER MIX WITHIN SAID FREE SPACE AND TO THE INTERIOR BOTTOM OF SAID CONTAINER-ELECTRODE. 